Usually crawler chains comprising chain links are guided between two track rollers. If a crane or an excavator with a crawler chassis with a crawler chain is moved on uneven terrain, problems can arise however, particularly in the case of depressions and holes in the ground. If the crane for example is turned on the spot and in that case the crawler chain sags in the centre precisely at the location of the depression in the ground, then the situation can occur where the track roller rides up on to the projection of the crawler chain. The projections of the crawler chain usually serve for guiding the crawler chain between the track rollers.
The same thing can occur if the crane turns on slightly inclined terrain In this case also there is the danger of the crawler chain being positioned inclinedly relative to the track roller, whereby the track roller can ride up on to the projection of the crawler chain as the track roller, by way of the projections, entrains the ground-engaging plate of the crawler chain, but that remains on the ground.
In the situations just discussed above therefore the crawler chain and the track rollers can suffer from damage, although various approaches are already known in this respect for reducing the loadings on the crawler chains and wear thereof.
Thus for example DE 100 36 367 A1 describes a crawler chassis which has a crawler carrier and at least one drive tumbler which can be fixed thereto, an idler wheel, an endless chain, a plurality of track rollers arranged at the lower run, and a direction-changing roller mounted in a mounting support. In order to alleviate stress peaks on the endless chain and thus to be able to prolong the service life of the crawler chain or reduce the wear thereof, the direction-changing roller is supported resiliently. That however only resolves the problem of avoiding high loadings on the crawler chain when rigging the crane insofar as a rigid arrangement of the drive tumbler and the idler wheel is used and the stress peaks which occur in that situation are reduced.
DE 36 03 261 A1 describes a further crawler chassis for bulldozers, loading crawler tractors or the like, wherein the aim is to resolve the problem of maintenance of the mountings of the running gear frame of the crawler chassis. Spherical mountings are used for that purpose, which are intended to reduce shock loadings on the chassis and achieve good damping. However loadings which act directly on the crawler chain are not addressed.
In addition DE 101 32 903 A1 discloses a crawler chassis for excavators, in particular for large hydraulic excavators, which has a crawler carrier accommodating a crawler chain, at least one chain wheel and at least one idler wheel, between which the crawler chain is guided if required by way of guide elements and over which the crawler chain can be deflected, and at least one tensioning element for the crawler chain. That arrangement is intended to reduce wear of the crawler chain. For that purpose the idler wheel is of a larger diameter than the chain wheel and the crawler chain is guided in the upper run substantially rectilinear between the idler and chain wheels. However, here too no solution is put forward, which would make it possible to avoid damage to the crawler chain and the track wheels if the crawler chassis is used on sloping or uneven terrain so that there is the danger of the track wheels running up on to the projections of the crawler chain.
JP 09254836 A shows a rolling wheel for a rubber crawler. Here, a pair of disk-like rolling members is disposed on a rolling wheel and arranged such that the rolling members roll beside projections of the rubber crawler. The rolling members have inclined surfaces formed according to the inclination of the sides of the projections. The rolling members are adapted to freely rotate coaxially with the rotating shaft of the rolling wheel, and installed opposite to the right and left sides of the projections. Accordingly, if lateral forces act between the rolling wheel and the rubber crawler, the side surface of the projections and the rolling members come into contact with each other, and the contact force can be softened because the rolling members are freely rotateable, though that the mutual abrasion can be reduced.
In U.S. Pat. No. 6,726,293 B2 a star carrier roller assembly is disclosed used in certain tracked mobile machines. The shown star carrier roller assembly includes a carrier roller positioned adjacent to a sprocket having a plurality of teeth. The sprocket is attached to the carrier roller to ensure rotation of the carrier roller even if undesirable substances become attached quite often inhibiting rotation of the carrier rollers. Such a stair carrier roller assembly should limit the wear of the carrier roller.
JP 05039065 A shows a wheel slip-off preventing mechanism for a rubber crawler. Here, a wheel slip-off preventing mechanism comprises a supporting part perpendicular to the longitudinal direction of a rubber crawler. The supporting part is installed on machine body, and a swing member which can move at least in the vertical direction is fitted on the supporting part. The swing member is installed between a pair of angular parts projecting on the inner peripheral surface of the rubber crawler or having the angular part interposed. The supporting part is a shaft body, and the swing member fitted on the; shaft body is fitted with a free hole having a large diameter than the thickness of the shaft body. The swing member travels in contact with the inner peripheral surface of the rubber crawler, and even in the case with the rubber crawler and the machine body are relatively separated in comparison with the contacting travelling, the swing can follow the rubber crawler inside.
A crawler belt slippage preventing structure is disclosed in JP 10035549 A. This known crawler belt slippage preventing structure comprises a plurality of Y-shaped branched crawler belt slippage preventing projections formed in the center part of a crawler belt. A pair of front and rear lower side rolling wheels is arranged in the lower part of a frame through a rolling wheel swing motion supporter. Projecting fitting recess parts in which the crawler belt slippage preventing projections are fitted, are formed between rolling wheel main bodies. An elastic crawler belt slippage preventing body is suspended between a pair of front and rear rolling wheel supporting boss parts of the rolling wheel swing motion supporter. A swelled part of the crawler belt slippage preventing body is arranged between the crawler belt slippage preventing projections and brought into contact with the inner circumferential surface of the crawler belt main body, so that the crawler belt can be prevented from being slipped from the lower side rolling wheels.
JP 10119834 A shows a running crawler guide. The running crawler guide comprises a pair of front rolling wheels and a pair of rear rolling wheels. Each pair of rolling wheels is vertically movable. A vertically movable guiding body is provided between the front and rear rolling wheels. The guiding body projects between projections formed on the rail of the crawler track.
Finally, JP 61064588 A shows a track roller of a crawler travelling apparatus. Outer collars are integrally formed onto the both outer sides of a roller and arranged so as to be positioned onto the both outer sides of a pair of projections arranged in parallel on the rail of the crawler at the center of a crawler. A middle collar is concentrically formed integrally with the both outer collars so as to be positioned in the cavity between the pair of projections.